Method for operating a cooking hob, and cooking hob

ABSTRACT

A gas cooking hob and a method of operating the hob including at least two physical cooking points and at least one electronic control component. A second one of the two cooking points located at a greater distance from the electronic control component than the first cooking point. The first cooking point is rendered inoperational or its calorific output is reduced when a first threshold temperature of the electronic control component is exceeded. The second cooking point is remains operational or its calorific output remains unchanged.

The present invention relates to a cooking hob, in particular a gascooking hob and a method for operating the cooking hob with at least twocooking points and with at least one electronic control component, ofwhich cooking points at least a second cooking point is at a greaterdistance from the electronic component than a first cooking point.

A method for operating a cooking hob is known, in which the gas burnersare turned off to protect electronic components of the gas cooking hobfrom overheating, whenever the temperature of the electronic componentsexceeds a threshold temperature. The threshold temperature correspondsto the maximum permissible temperature, and when this is exceeded thereis the danger of overheating of the electronic components.

The object of the present invention comprises providing a cooking hob,in particular a gas cooking hob, as well as a method for operating acooking hob, in order to improve its serviceability.

The task of the invention is solved by a method having the features ofClaim 1. According to the characterising part of Claim 1 in the methodthe first cooking point nearest to the electronic component is assigneda threshold temperature independently of the second cooking point.

Whenever the temperature of the electronic component exceeds thisthreshold temperature, only the nearest first cooking point is renderedinoperational to protect from overheating of the electronic component orrespectively its calorific output is reduced. The second cooking pointby comparison remains serviceable for a user.

According to the present invention in gas cooking hobs it has provenparticularly advantageous if the second cooking point, that is, thesecond gas burner, remains operational. In this case namely a primaryair flow to the second gas burner supports effective cooling of theelectronic component. The primary air flow occurs when convection airfrom the environment is suctioned into the gas supply line leading tothe gas burner.

The following embodiments aimed at gas cooking hobs also apply ingeneral similarly for electro-cooking hobs with corresponding cookingpoints: according to a particular embodiment the threshold temperaturecan be in a magnitude of ca. 20 K below a permissible maximumtemperature. The latter may not be exceeded with a thermal load of theelectronic component. The first cooking point is therefore alreadyswitched off before the maximum temperature is reached or respectivelyreduced in its calorific output. In this way despite operation of thefurther removed cooking point the component temperature does not rise tomaximum temperature.

To boost serviceability of the gas cooking hob it is an advantage if theoperability or respectively the calorific output of the first cookingpoint is still made or respectively reset during the cooking hoboperation. This means that while other gas burners are in operation, theresetting of the first gas burner takes place. In a particularly simpleway in terms of circuit technology the electronic control unit of thegas cooking hob can therefore be assigned a time function element. Thetime function element prevents resetting of the first gas burner untilsuch time as a preset cooling interval has expired.

The length of the cooling interval can be predetermined as follows:first a variation in time of the component temperature is detecteddirectly after it enters the cooling interval. On the basis of thedetected variation in time the length of the time interval ispredetermined.

Alternatively and/or in addition the angle of inclination of thevariation in time of the component temperature can also be monitored onan ongoing basis: if the component temperature falls at an angle ofinclination, which is greater than a predetermined angle of inclinationstored in the control unit, resetting of the first gas burner takesplace.

In terms of safety engineering it is particularly advantageous ifresetting of the first gas burner takes place as soon as the componenttemperature again falls below the threshold temperature. In particularthe first gas burner can be reset if the component temperature fallsbelow a lower threshold temperature below the threshold temperature.This is advantageous with virtually continuous measuring of thecomponent temperature. With continuous measuring the measuredtemperature values can fluctuate within a tolerance band about anaverage component temperature. The lower threshold temperature liesaround this tolerance band below the actual threshold temperature.Constant on/off switching of the gas burner is thus prevented if thecomponent temperature moves in the vicinity of the thresholdtemperature.

It is particularly operation-friendly if before any such exceeding oftemperature the calorific output of the first gas burner corresponds tothe threshold temperature of the calorific output after any such fallingbelow of threshold temperature. This is easily achievable in particularwith so-called fully-electronic gas cooking hobs. With fully-electronicgas cooking hobs the power stage of a cooking point can be stored byelectronic control unit. With switching on again of the first gas burnerthe stored power stage of the first gas burner is automatically reset bymeans of the electronic control unit.

After successful reduction in calorific output at the cooking point ifthe component temperature curve does not sink, further measures can betaken to protect from overheating of the electronic component: it isadvantageous if the first cooking point is completely switched off.

If the component temperature curve does not sink even after the firstgas burner is switched off, in addition the second gas burner can beswitched to inoperative or respectively reduced in its calorific output.This measure can be undertaken in a technically simple manner, if thecomponent temperature is still over the threshold temperature after aspecific time period.

Similarly to the first gas burner the second gas burner can also beassigned its own second threshold temperature. The latter is above thefirst threshold temperature. If the component temperature exceeds thesecond threshold temperature, in addition the second gas burner isrendered inoperational or respectively its calorific output is reduced.This variant is preferred in terms of safety technology, since thesecond gas burner is actuated only when the assigned thresholdtemperature is actually exceeded.

The serviceability of the gas cooking hob can be raised further, whenits own threshold temperature is assigned in each case to each of thegas burners of the gas cooking hob.

The values of the assigned threshold temperatures rise with increasingdistance of the burner from the electronic component. Insofar as thecomponent temperature exceeds one of the threshold temperatures, theassigned gas burner is rendered inoperational or respectively itscalorific output is reduced. In the case of a rising componenttemperature once the temperature drops below the first thresholdtemperature first the first gas burner is switched off or respectivelyits calorific output is reduced. The further away gas burners in seriesare then switched off also or respectively their calorific outputs arereduced. The threshold temperature of the gas burners farthest from theelectronic component can be set in the vicinity of the maximumpermissible temperature for the electronic component.

Four embodiments of the invention will now be described hereinbelow withreference to the accompanying figures, in which:

FIG. 1 is a gas cooking hob in a plan view;

FIG. 2 is a side elevation along line 1—1 of Figure;

FIG. 3 is a block diagram of the gas cooking hob according to the firstembodiment;

FIG. 4 is a diagram stored in an electronic control unit of the gascooking hob;

FIG. 5 is a temperature and operability diagram according to the firstembodiment;

FIG. 6 is a block diagram as per FIG. 3 according to the secondembodiment;

FIG. 7 is a temperature and calorific output diagram according to thesecond embodiment;

FIG. 8 is a temperature and calorific output diagram according to thethird embodiment; and

FIG. 9 is a temperature diagram according to the fourth embodiment.

FIG. 1 illustrates a gas cooking hob set in a section of a work surface.The gas cooking hob has four gas burners 1, 2, 3, 4. The gas burners areoperated by a control knob 7 provided in a front control panel 6. Asindicated in FIG. 2, above the gas burner grids 8 are arranged, on whichcooking goods containers (not illustrated here) can be set. According toFIG. 2 the gas cooking pan has a floor pan 9 with high side walls 10.Attached to the side walls 10 of the floor pan 9 is a cover plate 11.The cover plate 11 sits with its outer periphery on the work surface 1.The gas burners 1, 2, 3, 4 protrude through assembly openings providedin the cover plate 11. Together with the cover plate 11 the floor pan 9delimits a trough interior 12, in which are arranged electroniccomponents, such as an ignition device 13 or a control unit 14 for thegas burner.

Built into the rear side wall 10 of the floor pan 9 are primary airopenings 15. Convection air flows through the latter into the troughinterior 12. The convection air serves as primary air supply for airsuction areas 16 on gas nozzles 17 of the gas burner. A flow path ofconvection air is indicated in FIG. 2 by means of arrows I. For theelectronic components 13, 14 to be cooled they are arranged in the flowpath I.

In the block diagram of FIG. 3 the functional connection between thecomponents 13, 14 with the gas burner 1 is shown. The other gas burners2 to 4 are connected identically to the components 13, 14. Accordinglythe gas burner 1 is supplied with gas via a gas supply line 21. In thegas supply line 21 an electromagnetic safety valve 22 is arranged, whichis opened or closed by the electronic control unit 14. The gas volumeflow required for desired burner heat capacity in the gas supply line 21can be adjusted by a gas tap 23. The gas tap 23 is to be actuated by thecontrol knob 13. The control knob 13 is also coupled to a signal emitter25, which is in signal connection via lines 27 with the electroniccontrol unit 14.

A thermoelement 29, which detects the presence of a flame on the gasburner 1, is assigned to the gas burner 1 for flame monitoring. Theelectronic control unit 14 is also connected by signal via a line 29 tothe ignition device 13. The latter controls an ignition electrode 18 forthe purpose of igniting a flame on the gas burner 1.

To start up the gas burner 1 a pressure and/or rotary motion is exertedon the control knob 13. This effectively generates corresponding signalsfrom the signal emitter 25 and sends them via the lines 27 to theelectronic control unit 14. The electronic control unit 14 detects thesignals of the signal emitter 25 and controls the ignition device 13accordingly. At this point their ignition electrode 18 ignites a flameon the gas burner 1. At the same time the electronic control unit 14contacts the interim closed safety valve 22 with a current from anexternal source. Via the current from an external source the safetyvalve 22 is opened and therefore also the gas supply line 3 to the gasburner 1. On completion of gas ignition on the gas burner 1 thethermoelement 27 is heated by the flame of the gas burner 1. Thethermocurrent thus generated on the thermoelement 27 assumes thefunction of the current from an external source and holds the safetyvalve 22 open in its place. After extinguishing of flames on the gasburner 1 the thermoelement cools off, whereby no further thermocurrentis produced. The result is that the electronic control unit 14 closesthe safety valve 22 and the gas supply line 21 to the gas burner 1 isblocked.

According to the present invention in FIG. 3 the electronic control unit14 is connected to a temperature sensor 33. The temperature sensor 33detects a temperature T_(K) in the region of the electronic components13, 14. The detected temperature T_(K) is compared to thresholdtemperature T₁, T₂, T₃, T₄ stored in the control unit 14.

According to the diagram from FIG. 4 each of the threshold temperaturesT₁, T₂, T₃, T₄ is assigned to one of the four gas burners 1, 2, 3, 4.From the diagram of FIG. 4 it emerges that the values of the storedthreshold temperatures T₁, T₂, T₃, T₄ increase with increasing distanceof the gas burner from the electronic components 13, 14. Accordingly alower threshold temperature T₁ of 90° C. is assigned to the gas burner 1nearest to the electronic components 13, 14.

Assigned to the gas burner 4 farthest away from the electroniccomponents 13, 14 is an upper threshold temperature T₄ of 110°. Theupper threshold temperature T₄ is approximately in a range which isreached at a maximum permissible thermal load of the components 13, 14.

A variation in time of the temperature T_(K) of the electroniccomponents 13, 14 measured by temperature sensor 33 is shown in thetemperature diagram of FIG. 5: accordingly, the component temperatureT_(K) first rises constantly to the beginning of the burner operationafter the time point t₀ until the first threshold temperature T₁ isexceeded. This is assigned to the first gas burner 1. In this case thesafety valve 22 is triggered and closed in the gas supply line 21 to thefirst gas burner 1 by the electronic control unit 14. The first gasburner 1 is thus rendered inoperational from the time point t₁, as isevident from the operability diagram of FIG. 5 below. Because ofswitching off the first gas burner 1 the component temperature T_(K)rises further after time point t₁, less strongly, until at time point t₂the second threshold temperature T₂ is exceeded. This is assigned to thesecond gas burner 2. Accordingly at time point t₂ the electronic controlunit 14 closes the safety valve 22 of the second gas burner 2. As aresult after the time point t₂ the component temperature T_(K) runsbelow the threshold temperatures T₃, T₄ of both remaining gas burners 3,4. The gas burners 3, 4 therefore remain operational. At time point t₃the component temperature T_(K) again drops below the second thresholdtemperature T₂. The electronic control unit 14 therefore again releasesthe safety valve 22 of the second gas burner 2 at time point t₃. Thesecond gas burner 2 can therefore be brought back into operation withcorresponding actuation of the assigned control knob 13. At time pointt₄ the component temperature T_(K) also drops below the first thresholdtemperature T₁. The electronic control unit 14 therefore also againreleases the safety valve 22 of the first gas burner 1 from time pointt₄.

In the second embodiment of FIGS. 6 and 7 power setting of the gasburners 1, 2, 3, 4 takes place not by means of has taps 23, but via thecontrol valve arrays 35. The gas control valve arrays 35 are connectedbetween the electronic control unit 14 and each of the four gas burners1, 2, 3, 4.

For illustration in FIG. 7 only the gas control valve array 35 connectedin between the gas burner 1 and the control unit 14 is shown. The latteris arranged in the gas supply line 21 and has four parallel partial gaslines, through which in each case a partial gas current flows. Anelectromagnetic control valve 37 with downstream throttle 39 is arrangedin each of the partial gas lines. Their throttle diameters can bedistinguished from one another. Downstream of the throttles 39 thepartial gas lines are recombined in the gas supply line 21. Depending onthe power stage adjusted by the operator the control unit 14 opens oneor more of the control valves 37 in the parallel partial gas lines. Themagnitude of the gas flow exiting from the gas control valve array 35 tothe gas burner 1 therefore matches the number of opened control valves37.

In FIG. 7 gas cooking hob operation according to the second embodimentis shown by means of a temperature and calorific output diagram.According to the lower calorific output diagram at time point t₀ allfour gas burners 1, 2, 3, 4 are in operation at different calorificoutputs P₁, P₂, P₃, P₄. The component temperature T_(K) rises constantlyafter time point t₀. At time point t₁, the component temperature T_(K)exceeds the first threshold temperature T. The four control valves 37 ofthe first gas burner 1 are accordingly closed from the time point t₁.

At the same time the control unit 14 stores the settings of the controlvalves 37 of the gas burner 1 at time point t₁. At time point t₂ thecomponent temperature T_(K) exceeds the second threshold temperature T₂.The electronic control unit 14 accordingly closes all control valves 37of the second gas burner 2 and at the same time stores their settings.At time point t₃ the component temperature T_(K) however falls below thesecond threshold temperature T₂. The electronic control unit 14therefore controls the control valves 37 of the second gas burner 2according to their stored settings. The second gas burner 2 is thereforeoperated again from time point t₃ with its calorific output P₂. Insimilar fashion at time point t₄ also the first gas burner 1 is put backinto operation.

In FIG. 8 a temperature und calorific output diagram is shown accordingto the third embodiment. The structure of the gas cooking hob of thethird embodiment is similar to the gas cooking hob of the secondembodiment. As shown in the calorific output diagram of FIG. 8, directlyafter the temperature drops below one of the threshold temperatures T₁,T₂, T₃, T₄ a cooling interval t_(a), t_(b) for the switched off gasburner is previously determined. To determine the length of the coolinginterval t_(a) the component temperature T_(K) is first determined in atime span a of the curve trajectory. The time span a begins directlyafter the component temperature T_(K) has exceeded the thresholdtemperature T₁. By way of the curve trajectory of the componenttemperature T_(K) determined in the time span a the electronic controlunit 14 determines the length of the cooling interval t_(a) for the gasburner 1. On expiry of the cooling interval t_(a) the first gas burner 1is again operated with its stored calorific output P₁. Likewise thelength of the time interval t_(b) for the second gas burner 2 isdetermined, after the component temperature T_(K) has exceeded thesecond threshold temperature T₂.

Alternatively or in addition the gas burner switched inoperational canalso then be rendered operational again whenever the componenttemperature T_(K) falls at an angle of inclination α, which is greaterthan a preset angle of inclination. The preset angle of inclination isstored in the control unit 14. According to the temperature diagram ofFIG. 9 at the time point t₁ the angle of inclination α is detected. Thedetected angle of inclination α is greater than the stored angle ofinclination. As a result the control unit 14 renders the first gasburner 1 operational again immediately, even before the componenttemperature T_(K) has fallen back to below the uncritical thresholdtemperature T₁.

1. A method for operating a gas cooking hob, the cooking hob includingat least two cooking points and at least one electronic controlcomponent, of which at least the second cooking point is further awayfrom the electronic control component than the first cooking point,comprising: sensing the temperature of the electronic control component;one of rendering the first cooking point inoperational or reducing thecalorific output of said first cooking point when a first predeterminedthreshold temperature is sensed; and one of continuing to operate thesecond cooking point or maintaining said second cooking point calorificoutput unchanged when said first predetermined threshold temperature issensed.
 2. The method according to claim 1, including said electroniccontrol component has a predetermined maximum permissible thermal loadand said first predetermined threshold temperature is in a magnitude ofabout ca. 20 K below a temperature range reached at said predeterminedmaximum permissible thermal load.
 3. The method according to claim 1,including resetting one of the operability or the calorific output ofsaid first cooking point during operation of the cooking hob.
 4. Themethod according to claim 3, including said resetting of one of theoperability or the calorific output of said first cooking point duringoperation of the cooking hob occurs following the expiration of a presetcooling interval.
 5. The method according to claim 4, includingpresetting the length of said preset cooling interval by the variationin time of the temperature of said electronic control component directlyafter said electronic control component enters said cooling interval. 6.The method according to claim 5, including presetting an angle ofinclination of said variation in time of said temperature of saidelectronic control component and resetting one of said operability orsaid calorific output of said first cooking point when said variation intime of said temperature of said electronic control component falls atan angle of inclination greater than said preset angle of inclination.7. The method according to claim 4, including a second predeterminedthreshold temperature lower than said first predetermined thresholdtemperature and resetting said one of said operability or said calorificoutput of said first cooking point when said temperature of saidelectronic control component falls below said second predeterminedthreshold temperature.
 8. The method according to claim 4, includingmeasuring said calorific output of said first cooking point andresetting said first cooking point to the measured calorific outputbefore said temperature of said electronic control component before saidfirst predetermined threshold temperature is exceeded.
 9. The methodaccording to claim 1, including reducing said calorific output of saidfirst cooking point when said first predetermined threshold temperatureis sensed and then switching off said first cooking point if saidtemperature of said electronic control component still exceeds saidfirst predetermined threshold temperature.
 10. The method according toclaim 1, including additionally one of rendering said second cookingpoint inoperational or reducing the calorific output of said secondcooking point if said temperature of said electronic control componentstill exceeds said first predetermined threshold temperature after apredetermined time period.
 11. The method according to claim 1,including a second predetermined threshold temperature which exceedssaid first predetermined threshold temperature and includingadditionally one of rendering said second cooking point inoperational orreducing said calorific output of said second cooking point if saidtemperature of said electronic control component exceeds said secondpredetermined threshold temperature.
 12. The method according to claim1, including a plurality of stored predetermined threshold temperaturesand including one of rendering one of said cooking points inoperationalor reducing said calorific output of said cooking point if saidtemperature of said electronic control component exceeds at least one ofsaid predetermined threshold temperatures.
 13. The method according toclaim 12, including a plurality of cooking points and assigning each ofsaid plurality of stored predetermined threshold temperatures to one ofsaid cooking points and increasing the value of said storedpredetermined threshold temperatures in accordance with the distance ofeach said cooking point from said electronic control component.
 14. Themethod according to claim 1, including directing a primary air flow tosaid plurality of cooking points and arranging said electronic controlcomponent in said primary air flow for cooling said electronic controlcomponent.
 15. A gas cooking hob, comprising: at least two cookingpoints; at least one electronic control component with at least a secondcooking point located further away from said electronic controlcomponent than a first cooking point; a sensor for sensing thetemperature of said electronic control component; said electroniccontrol component one of renders said first cooking point inoperationalor reduces the calorific output of said first cooking point when saidsensor senses a first predetermined threshold temperature; and saidelectronic control component one of continues to operate said secondcooking point or maintains said second cooking point calorific outputunchanged when said sensor senses said first predetermined thresholdtemperature.
 16. The gas cooking hob according to claim 15, includingsaid electronic control component resets one of the operability or thecalorific output of said first cooking point during operation of thecooking hob.
 17. The gas cooking hob according to claim 16, includingsaid electronic control component resets one of said operability or saidcalorific output of said first cooking point during operation of saidcooking hob following the expiration of a preset cooling interval. 18.The gas cooking hob according to claim 17, including a secondpredetermined threshold temperature lower than said first predeterminedthreshold temperature and said electronic control component resets saidone of said operability or said calorific output of said first cookingpoint when said temperature of said electronic control component fallsbelow said second predetermined threshold temperature.
 19. The gascooking hob according to claim 15, including said electronic controlcomponent reduces said calorific output of said first cooking point whensaid first predetermined threshold temperature is sensed and thenswitches off said first cooking point if said temperature of saidelectronic control component still exceeds said first predeterminedthreshold temperature.
 20. The gas cooking hob according to claim 15,including a plurality of stored predetermined threshold temperatures andincluding said electronic control component one of renders one of saidcooking points inoperational or reduces said calorific output of saidcooking point if said temperature of said electronic control componentexceeds at least one of said predetermined threshold temperatures andassigning each of said plurality of stored predetermined thresholdtemperatures to one of said cooking points and increasing the value ofsaid stored predetermined threshold temperatures in accordance with thedistance of each said cooking point from said electronic controlcomponent.